Device and method for locking a screw with a bendable plate portion

ABSTRACT

A spinal device for stabilizing adjacent vertebral bodies of the human spine. The device includes a combination of a screw and a member having a screw hole and a length sufficient to span a disc space between the adjacent vertebral bodies. The member has a portion that is bendable or deformable to prevent the outward excursion of the screw from the screw hole of the member.

The present application is a continuation of application Ser. No.13/180,990, filed; Jul. 12, 2011; which is a continuation of applicationSer. No. 10/105,773, filed Mar. 25, 2002; now U.S. Pat. No. 7,976,566,which is a continuation of application Ser. No. 09/563,705, filed May 2,2000, now U.S. Pat. No. 6,364,880; which is a continuation ofapplication Ser. No. 09/126,585, filed Jul. 31, 1998, now U.S. Pat. No.6,136,001; which is a continuation of application Ser. No. 08/926,334,filed Sep. 5, 1997, now U.S. Pat. No. 6,120,503; which is a continuationof application Ser. No. 08/589,787, filed Jan. 22, 1996, now abandoned;which is a continuation of application Ser. No. 08/219,626, filed Mar.28, 1994, now abandoned; all of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to surgical interbody fixation devices and inparticular to a surgically implantable device for the stabilization ofadjacent vertebrae of the human spine undergoing spinal arthrodesis andfor the prevention of the dislodgement of spinal fusion implants used inthe fusion process.

2. Description of the Related Art

When a segment of the human spine degenerates, or otherwise becomesdiseased, it may become necessary to surgically remove the affected discof that segment, and to replace it with bone for the purpose ofobtaining a spinal fusion by which to restore more normal, pre-morbid,spatial relations, and to provide for enhanced stability across thatsegment. Performing such surgery of the spine from an anterior (front)approach offers the great advantage of avoiding the spinal cord, duralsac, and nerve roots. Unfortunately, in entering the disc spaceanteriorly a very important band-like structure called the anteriorlongitudinal ligament, is violated. This structure physiologically actsas a significant restraint resisting the anterior displacement of thedisc itself and acting as a tension band binding the front portions ofthe vertebrae so as to limit spinal hyperextension.

Historically, various devices have been utilized in an attempt tocompensate for the loss of this important stabilizing structure. Thesedevices have assumed the form of blocks, bars, cables, or somecombination thereof, and are bound to the vertebrae by screws, staples,bolts, or some combination thereof. The earliest teachings are of ametal plate attached to adjacent vertebrae with rood-type screws. Dwyerteaches the use of a staple-screw combination. Brantigan U.S. Pat. No.4,743,256 issued on May 10, 1988, teaches the use of a block inserted toreplace the disc, affixed to a plate then screwed to the vertebrae aboveand below. Raezian U.S. Pat. No. 4,401,112 issued on Aug. 30, 1993,teaches the use of a turnbuckle affixed to an elongated staple such thatat least one entire vertebral body is removed, the turnbuckle portion isplaced within the spine, and the staple extends both above and below theturnbuckle and engages the adjacent vertebrae to the one removed.

Unfortunately, both staples and screws have quite predictablydemonstrated the propensity to back out from the vertebrae. This isquite understandable as any motion, either micro or macro, tends tostress the interface of the metallic implant to the bone, and in doingso causes the bone to relieve the high stress upon it by resorbing andmoving away from the metal. This entropic change is universally from themore tightened and thus well-fixated state, to the less tightened andless fixated state. For a staple, this is specifically from the morecompressed and engaged state, to the less compressed and disengagedstate. Similarly, screws in such a dynamic system loosen and back out.

The potential consequences of such loosening and consequent backing outof the hardware from the anterior aspect of the vertebral column mayeasily be catastrophic. Because of the proximity of the great vessels,aortic erosions and perforations of the vena cava and iliac vessels haveusually occurred with unfortunate regularity and have usually resultedin death.

Therefore, the need exists for a device which is effective in restoringstability to a segment of the spine such as, but not limited to, theanterior aspect of the human spine and which will without danger remainpermanently fixated once applied.

SUMMARY OF THE INVENTION

The present invention is directed to a spinal fixation device forstabilizing a segment of the human spine and for preventing thedislodgement of intervertebral spinal fusion implants, which remainspermanently fixated to the spine once applied. The spinal fixationdevice of the present invention comprises a staple member made of amaterial appropriate for human surgical implantation and which is ofsufficient length to span the disc space between two adjacent vertebrae.The staple member engages, via essentially perpendicular extendingprojections, the vertebrae adjacent to that disc space. The projectionsare sharpened and pointed so as to facilitate their insertion into thevertebrae and are segmented or ratcheted to prevent the staple memberfrom disengaging and backing out once inserted.

In the preferred embodiment of the spinal fixation device of the presentinvention, a portion of the staple member interdigitates with an alreadyimplanted intervertebral spinal fusion implant and the staple member isbound to the spinal fusion implant by a locking mechanism such as ascrew with a locking thread pattern. The anchoring of the staple membervia a locking mechanism to a spinal fusion implant protects the patientfrom the danger of the staple member itself disengaging and backing out.Further, if the spinal fusion implant is externally threaded, such asthe spinal fusion implant taught by Michelson, U.S. Pat. No. 5,015,247issued on May 14, 1991, then the staple member could only back out ifthe spinal fusion implant were free to rotate. However, the rotation ofthe spinal fusion implant in this instance is blocked by its connectionto the staple member which is fixated across the disc space in such away as to be incapable of rotation. Thus, the staple member is made safeagainst dislodgement by attachment to the spinal fusion implant and thestability of the spinal fusion implant is assured as it is alsostabilized by the staple member and each works in connection with theother to remove the only remaining degree of freedom that would allowfor the disengagement of either.

The spinal fixation device of the present invention is broadlyapplicable to the anterior, posterior and lateral aspects of the spinalcolumn, be it the cervical, thoracic or lumbar area. In particular, theuse of a staple member spanning the disc space and engaging the adjacentvertebrae which is applied to the anterior aspect of the spine is ofgreat utility in restraining those vertebral bodies from moving apart asthe spine is extended and thus is effective in replacing the anteriorlongitudinal ligament of the patient.

The spinal fixation device of the present invention provides theadvantage of facilitating cross vertebral bony bridging (fusion viaimmobilization) which when achieved relieves all of the forces on theinserted spinal fusion implants. The spinal fixation device of thepresent invention may be coated with materials to promote bone fusionand thus promote the incorporation and ultimate entombment of the spinalfixation device into the bone fusion mass. The use of a bone fusionpromoting material results in a speedier vertebra to vertebra fusion asbone may grow along the coated spinal fixation device bridging the twovertebrae so that the spinal fixation device acts as a trellis andsupplies essential chemical elements to facilitate the bone fusionprocess.

Another advantage provided by the spinal fixation device of the presentinvention is that as it is inserted it compresses the adjacent vertebraetogether, thus increasing the compressive load on the spinal fusionimplants or implants within the disc space, such compression beingbeneficial to fusion and further stabilizing the spinal fusion implants.

A further advantage of the spinal fixation device of the presentinvention is that it may be used as an anchor such that a multiplicityof spinal fixation devices may then be interconnected via a cable, rod,bar, or plate, so as to achieve or maintain a multi-segmental spinalalignment.

Alternatively, the spinal fixation device of the present invention couldbe made of resorbable materials, such as bio-compatible resorbableplastics, that resorb at an appropriate rate such that once the spinalfixation device is no longer needed (i.e. when spinal fusion iscomplete) the body would resorb the spinal fixation device. The spinalfixation device could be only in part resorbable such that theprojections of the staple member would be non-resorbable and wouldremain incarcerated in the vertebrae and sealed off once the resorbableportion of the staple is resorbed by the body.

As a further alternative, the spinal fixation device of the presentinvention could be made wholly of in part of ceramic and moreparticularly made of or coated with a ceramic such as hydroxyapatitethat would actively participate in the fusion process.

OBJECTS OF THE PRESENT INVENTION

It is an object of the present invention to provide a spinal fixationdevice having a staple member spanning the disc space and engaging twoadjacent vertebrae of the spine to restrain the vertebrae from movingapart as the spine is extended;

It is an another object of the present invention to provide a spinalfixation device that is effective in replacing the function of theanterior longitudinal ligament of a patient;

It is a further object of the present invention to provide a means forprotecting the patient from the danger of the spinal fixation deviceitself disengaging and backing out by its being anchored to anintervertebral spinal fusion implant;

It is still another object of the present invention to provide a spinalfixation device that blocks the rotation of an intervertebral spinalfusion implant by its connection to the staple member which is fixatedacross the disc space in such a way as to be incapable of rotationthereby preventing the spinal fusion implant from backing out;

It is yet another object of the present invention to provide a spinalfixation device that is broadly applicable to the anterior aspect of thespinal column, be it the cervical, thoracic or lumbar area;

It is another object of the present invention to provide a spinalfixation device which may be applied longitudinally at any point aboutthe circumference of the anterior aspect of the spine;

It is also another object of the present invention to provide a spinalfixation device that stabilizes a surgically implanted spinal fusionimplant and works in connection with the spinal fusion implant toprevent disengagement of either;

It is another object of the present invention to provide a spinalfixation device that achieves cross vertebral bony bridging (fusion)which ultimately relieves all of the forces on inter-vertebral spinalfusion implants inserted within the disc space between two adjacentvertebrae, and provides for a permanently good result;

It is another object of the present invention to provide a spinalfixation device that serves as an anchor, such that a multiplicity ofthese anchors may then be interconnected via a cable, rod, bar, orplate, so as to achieve or maintain a multi-segmental spinal alignment;and

It is a further object of the present invention to provide a spinalfixation device that directly participates in the bony bridging of twoadjacent vertebrae and participates in the spinal fusion process acrossthose vertebrae.

These and other objects of the present invention will become apparentfrom a review of the accompanying drawings and the detailed descriptionof the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective side view of a segment of the spinal columnhaving two spinal fusion implants shown partially in hidden lineinserted across the disc space between two adjacent vertebrae with eachspinal fusion implant having a spinal fixation device of the presentinvention shown partially in hidden line secured thereto, spanningacross the disc space and inserted into the vertebrae.

FIG. 2 is a perspective side view of a segment of the spinal columnhaving two spinal fusion implants inserted across the disc space betweentwo adjacent vertebrae.

FIG. 3 is an elevational side view of a cylindrical threaded spinalfusion implant.

FIG. 4 is an end view of the cylindrical threaded spinal fusion implantalong lines 4-4 of FIG. 3.

FIG. 5 is a perspective side view of a segment of the spinal columnhaving two non-threaded spinal fusion implants with externalratchetings, shown in hidden line, inserted across the disc spacebetween two adjacent vertebrae with each spinal fusion implant having aspinal fixation device of the present invention, shown partially inhidden line, coupled thereto, spanning across the disc space andinserted into the vertebrae.

FIG. 6 is a perspective side view of a segment of the spinal columnhaving two spinal fusion implants having truncated sides with externalratchetings shown in hidden line inserted across the disc space betweentwo adjacent vertebrae with each spinal fusion implant having a spinalfixation device of the present invention shown partially in hidden linecoupled thereto, spanning across the disc space and inserted into thevertebrae.

FIG. 7 is a perspective side view of a segment of the spinal columnhaving two spinal fusion implants having a knurled external surfaceshown in hidden line inserted across the disc space between two adjacentvertebrae with each spinal fusion implant having a spinal fixationdevice of the present invention shown partially in hidden line coupledthereto, spanning across the disc space and inserted into the vertebrae.

FIG. 8 is a top plan view of the spinal fixation device of the presentinvention.

FIG. 9 is a side view of the spinal fixation device of the presentinvention along lines 9-9 of FIG. 8.

FIG. 10 is a cross sectional view taken along lines 10-10 of FIG. 8showing the top member of the spinal fixation device of the presentinvention.

FIG. 11 is an enlarged fragmentary perspective side view of a projectionof the spinal fixation device of the present invention taken along line11 of FIG. 9.

FIG. 12 is a cross sectional view of the spinal fixation device of thepresent invention inserted into the vertebrae and secured to the spinalfusion implant with the arrows showing the forces exerted, therotational axis and the longitudinal axis of the spinal fusion implant.

FIG. 13A is a cross sectional view along line 13-13 of FIG. 9 of thepreferred embodiment of the projections of the present invention.

FIGS. 13B, 13C, 13D, 13E, and 13F are cross sectional views taken alongline 13-13 of FIG. 9 showing alternative embodiments of the projectionsof the spinal fixation device of the present invention.

FIG. 14 is an enlarged elevational side view of the locking screw usedto secure the spinal fixation device of the present invention to aspinal fusion implant.

FIG. 15A is a cross sectional view of a securing means for locking thelocking screw of the present invention.

FIG. 15B is a cross sectional view of a first alternative embodiment ofthe securing means for locking the locking screw of the presentinvention.

FIG. 15C is a cross sectional view of a second alternative embodiment ofthe securing means for locking the locking screw of the presentinvention.

FIG. 16A is a perspective side view of the instrumentation used fordriving the spinal fixation device of the present invention into thevertebrae.

FIG. 16B is a perspective side view of a first alternative embodiment ofthe instrumentation used for driving the spinal fixation device of thepresent invention into the vertebrae.

FIG. 17A is a perspective side view of an alignment rod used to alignthe spinal fixation device of the present invention.

FIG. 17B is a perspective side view of an alternative embodiment of thealignment rod having splines used to align the spinal fixation device ofthe present invention.

FIG. 18 is a front perspective view of the drill template instrument.

FIG. 19 is a perspective side view of the alignment rod attached to aspinal fusion implant inserted in the disc space between two adjacentvertebrae.

FIG. 20 illustrates the step of drilling guide holes in the vertebraeadjacent to the spinal fusion implant with the drill template instrumentof FIG. 18.

FIG. 21 illustrates a step of the method of inserting the spinalfixation device of the present invention with the alignment rod attachedto the spinal fusion implant and the spinal fixation device placed onthe driver instrumentation.

FIG. 22 illustrates a step of the short method of inserting the spinalfixation device of the present invention with the driver instrumentengaging the splined alignment rod and a hammer for applying animpaction force and driving the driver instrument.

FIG. 22A is an enlarged fragmentary view of a projection being insertedinto an insertion hole drilled within a vertebra shown in cross sectiontaken along line 22A of FIG. 21.

FIG. 23 illustrates another step of the method of inserting the spinalfixation device of the present invention in which the spinal fixationdevice has been driven into the vertebrae and the driver instrumentationhas been removed.

FIG. 24 illustrates another step of the method of inserting the spinalfixation device of the present invention with the splined alignment rodbeing removed from the spinal fusion implant and the locking screw beinginserted and secured the spinal fixation device to the spinal fusionimplant.

FIG. 25 is a top plan view of a first alternative embodiment of thespinal fixation device of the present invention.

FIG. 26 is a top plan view of a second alternative embodiment of thespinal fixation device of the present invention.

FIG. 27 is a perspective side view of a third alternative embodiment ofthe spinal fixation device of the present invention coupled to twospinal fusion implants and inserted in adjacent vertebrae of the spinalcolumn.

FIG. 28 is a top plan view of a fourth alternative embodiment of thespinal fixation device of the present invention inserted into thevertebrae of the spinal column having a spinal fusion implant insertedin the disc space.

FIG. 29 is a top plan view of a fifth alternative embodiment of thespinal fixation device of the present invention inserted into thevertebrae of the spinal column having a spinal fusion implant insertedin the disc space.

FIG. 30 is a perspective bottom view of the fourth alternativeembodiment of the spinal fixation device of the present invention.

FIG. 31 is a cross sectional view along lines 31-31 of FIG. 29 showingthe fifth alternative embodiment of the spinal fixation device of thepresent invention inserted into the adjacent vertebrae and coupled to aspinal fusion implant.

FIG. 32 is a cross sectional view along lines 32-32 of FIG. 29 showingthe projections of the fifth alternative embodiment of the presentinvention with respect to a spinal fusion implant inserted within thedisc space.

FIG. 33 is a cross sectional view of a spinal fixation device of thepresent invention engaging two adjacent vertebrae and being attached toa spinal fusion implant, shown being used as an anchor for amulti-segmental spinal alignment means.

FIG. 34 is an enlarged elevational side view of a threaded post used toconnect the spinal fixation device of the present invention to amulti-segmental spinal alignment means.

FIG. 35 is an exploded perspective view of a sixth alternativeembodiment of the spinal fixation device of the present invention havingindependent projection members that are screws.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, two identical spinal fixation devices of thepresent invention, each being generally referred to by the numerals 10and 11, respectively, are shown inserted into two vertebrae V adjacentto a disc D of a segment of the human spine. Each spinal fixation device10 and 11 is shown coupled to identical spinal fusion implants 40 and 41that have been surgically implanted in the disc space between adjacentvertebrae V. In this manner, the spinal fixation devices 10 and 11stabilize a segment of the spine, prevent the dislodgement of the spinalfusion implant 40, and remain permanently fixated to the spine onceapplied. The spinal fixation devices 10 and 11 are identical such thatthe description of one is equally applicable to the other. Thus, thedescription that follows will be directed to spinal fixation device 10.

Referring to FIGS. 3-4, the spinal fusion implant 40 such as, but notlimited to, the spinal fusion implant described by Michelson, U.S. Pat.No. 5,0165,247 issued on May 14, 1991, is shown. The spinal fusionimplant 40 is cylindrical in shape and has external threads 42 at itsouter perimeter for engaging the bone of the vertebrae V adjacent to thedisc D. The spinal fusion implant 40 has a trailing end 43 having adepression 44 and a threaded aperture 45 for engaging a portion of thespinal fixation device 10 and also for engaging a portion of aninstrument used to insert the spinal fixation device 10 into thevertebrae V.

Referring to FIGS. 5-7, it is appreciated that the spinal fixationdevices 10 and 11 of the present invention are not limited in use with athreaded spinal fusion implant 40 and 41, but may be used with differenttypes of spinal fusion implants. For example, the spinal fixationdevices 10 and 11 may be coupled to spinal fusion implants 40 a and 41a, respectively, each having external ratchetings 42 a instead ofexternal threads 42 as shown in FIG. 5. Alternatively, the spinalfixation devices 10 and 11 may be coupled to spinal fusion implants 40 band 41 b, respectively, each having a partially cylindrical shape withat least one truncated side 47 as shown in FIG. 6. As a furtheralternative, the spinal fixation devices 10 and 11 may be coupled tospinal fusion implants 40 c and 41 c, respectively, each having aknurled external surface 48 as shown in FIG. 7. It is also appreciatedthat the spinal fixation devices may be used with a variety of otherbone fusion implants without departing from the scope of the presentinvention.

Referring to FIGS. 8-9, in the preferred embodiment, the spinal fixationdevice 10 of the present invention comprises a staple member 12 having asubstantially planar top member 14 which is of sufficient length to spanone intervertebral disc D and to engage, via a plurality of essentiallyperpendicular extending projections 16 and 17, the vertebrae V adjacentto that disc D. The top member 14 has a central opening 18 within aconcentric, countersunk recess 19 for receiving therethrough a screw orsimilar coupling means for coupling the spinal fixation device 10 to thespinal fusion implant 40. The top member 14 has an upper surface 20having a pair of openings 22 a and 22 b for receiving the posts 88 a and88 b of a driving instrument 80 which is described in greater detailbelow in reference to FIGS. 16A and 16B.

Referring to FIG. 10, a cross sectional view of the top member 14 isshown. In the preferred embodiment, the top member 14 is generallytriangularly shaped and is radiused along curved side 24 and straightside 26. The curved side 24 of the top member 14 is radiused at itsupper edge 25 and at the upper edge 27 of straight side 26 to conform tothe external curvature of the vertebrae V. In this manner, smoothsurfaces are created at the upper edges 25 and 27 of the top member 14that are contoured to the shape of the external curvature of thevertebrae V when the staple member 12 is in place. The smooth contouredsurface of the upper edges 25 and 27 of the top member 14 prevent aorticerosions and perforations of the vessels proximate the vertebral columnsuch as the vena cava and the iliac vessels which might otherwise resultfrom friction.

In the preferred embodiment of the spinal fixation device 10, the topmember 14 has a width ranging from 6.0 mm to 28.0 mm, with 10.0 mm beingthe preferred width, and having a thickness in the range of 2.0 mm to4.0 mm, with 3.0 mm being the preferred thickness. The staple member 12is made of material appropriate for human surgical implantationincluding all surgically appropriate metals such as but not limited to,titanium, titanium alloy, chrome molybidium alloys, stainless steel; ornon-metallic materials including permanent or resorbable substances orcomposites, carbon fiber materials, resins, plastics, ceramics orothers.

Further, the staple member 12 of the present invention may be treatedwith, or even composed of, materials known to participate in or promotein the fusion process or bone growth. The spinal fixation device 10 maybe coated with materials to promote bone fusion and thus promote theincorporation and ultimate entombment of the spinal fixation device 10into the bone fusion mass. The use of a bone fusion promoting materialsuch as, but not limited to hydroxyapatite, hydroxyapatite tricalciumphosphate or bone morphogenic protein, results in a speedier vertebra Vto vertebra V fusion as bone may grow along the coated spinal fixationdevice 10 bridging the two vertebrae V so that the spinal fixationdevice 10 acts as a trellis and supplies essential chemical elements tofacilitate the bone fusion process.

Referring again to FIG. 9, the projections 16 and 17 are positioned atopposite ends of the top member 14 and depend downwardly and extendperpendicularly from the bottom surface 30 of the top member 14. Theprojections 16 and 17 each terminate in a distal end 32 that is pointedand sharpened to facilitate the insertion of the projections 16 and 17into the vertebrae V.

The staple member 12 is most effective when the interprojection distanceI between projections 16 and 17 is at least 4.0 mm and preferably 6.0 mmgreater than the diameter of the particular spinal fusion implant 40 forwhich the spinal fixation device 10 is being used so that at least 2.0mm and preferably 3.0 mm of bone from the vertebrae V will be presentbetween the spinal fusion implant 40 and each of the projections 16 and17. Typically, intervertebral spinal fusion implants have a diameterthat ranges from 12.0 mm to 28.0 mm, therefore, the interprojectiondistance I typically will range from 18.0 mm to 34.0 mm for mostapplications.

In the preferred embodiment, the projections 16 and 17 comprise a seriesof segmented and ratcheted portions 34. The segmented and ratchetedportions 34 provide for a “one way” insertion of the staple member 12 toprevent the backing-out of the projections 16 and 17 once they areinserted into the bone of the vertebrae V. In the preferred embodiment,each segmented and ratcheted portion 34 of the projections 16 and 17 isconical in shape and the diameter of each segmented and ratchetedportion 34 increases in the direction from the distal end 32 toward thetop member 14 so that the projections 16 and 17 resemble a stack ofcones. The segmented and ratcheted portions 34 are spaced approximately2.0 mm to 4.0 mm apart, with 3.0 mm being the preferred distance betweeneach segmented and ratcheted portion 34.

Referring to FIG. 11-12, in the preferred embodiment of the spinalfixation device 10, in order to further facilitate the insertion of theprojections 16 and 17 into the vertebrae V, the distal end 32 of eachprojection 16 has an eccentric, incline-planed inner surface 36 as shownin FIG. 11. The eccentric, incline-planed inner surface 36 of each ofthe projections 16 and 17 create a force F which pushes the bone of thevertebrae V toward the spinal fusion implant 40 as the staple member 12is inserted into each of the vertebrae V as shown in FIG. 12.

Referring to FIGS. 13A-13F, in the preferred embodiment of the spinalfixation device 10, the projections 16 and 17 are cylindrical in shapehaving a circular cross section as shown for projection 16 in FIG. 13A.Alternatively, the projection 16 a may have a triangular cross sectionas shown in FIG. 13B; the projection 16 b may have a square crosssection as shown in FIG. 13C; the projection 16 c may have a rectangularcross section as shown in FIG. 13D; the projection 16 d may have atrapezoidal cross section as shown in FIG. 13E; or the projection 16 emay have a cross section with a configuration as shown in FIG. 13F.

In the preferred embodiment, the projections 16 and 17 each have adiameter of approximately 2.0 mm to 4.0 mm, with 3.0 mm being thepreferred diameter at the widest point. The projection 16 and 17 eachhave a length ranging from 16.0 mm to 28.0 mm, with 22.0 mm being thepreferred length when the spinal fixation device 10 is implanted in thedirection of the anterior aspect of the vertebra V to the posterioraspect of the vertebrae V. Alternatively, it is appreciated that theprojections 16 and 17 each could have a longer length depending on thediameter of the vertebrae V in which the projections 16 and 17 areimplanted.

Referring again to FIG. 9, the top member 14 of the staple member 12 hasa central bar 35 extending from the center of its bottom surface 30, forinterdigitating and mating to an already implanted intervertebral spinalfusion implant 40. In the preferred embodiment, the central bar 35 has athickness in the range of 0.5 mm to 1.5 mm, with 0.5 mm being thepreferred thickness.

Referring to FIG. 1, the central bar 35 is configured so that itcomplements and engages the depression 44 at the insertion end 43 of thespinal fusion implant 40. Once engaged to the depression 44, the bar 35interdigitates with the depression 44 of the spinal fusion implant 40 tolock and prevent the rotation of the spinal fusion implant 40.

Referring to FIG. 14, in the preferred embodiment, the staple member 12is secured to the spinal fusion implant 40 by a screw 60 having threadedend 61 with a locking thread pattern 62 and screw head 64. The lockingthread pattern 62 has a reduced pitch at the bottom of the threaded end61 such that the screw 60 is self-locking. However, it is appreciatedthat the threaded pattern 62 may be any of the means for locking a screwwell known by those skilled in the art.

Referring to FIGS. 2 and 8, the threaded end 61 of the screw 60 passesthrough the central opening 18 of the top member 14 and the threadedpattern 62 threads into the threaded aperture 45 of the spinal fusionimplant 40. The screw head 64 fits within the countersunk recess 19 ofthe top member 14 such that the screw head 64 is at or below the planeof the upper surface 20 of the top member 14. In the preferredembodiment, the central opening 18 has a diameter ranging from 4.5 mm to5.5 mm, with 5.0 mm being the preferred diameter. The countersunk recess19 has a diameter in the range of 6.0 mm to 8.0 mm with 7.0 mm being thepreferred diameter.

Referring to FIGS. 15A, 15B, and 15C, an enlarged cross sectional viewof three different embodiments of a securing means 65 for locking thescrew 60 once it is threaded to the spinal fusion implant 40 are shown.In FIG. 15A, the securing means 65 comprises a notch 66 in the surface20 of the top member 14 which is preferably made of metal. Once thescrew 60 is threaded and securely tightened to the spinal fusion implant40, a chisel C is used to bend a portion 67 of the top member 14 intothe central opening 18 and against the screw head 64 so as to preventthe outward excursion and any unwanted loosening of the screw 60.

In FIG. 15B, a second embodiment of the securing means 65 a is showncomprising a central score 66 a concentric with the central opening 18.A screw 60 a having a slot 61 a in the screw head 64 a is threaded andsecurely tightened to the spinal fusion implant 40. An instrument T ispartially inserted into slot 61 a after which an impaction force F.sub.1is applied to the instrument T to spread apart the screw head 64 a inthe direction of the arrows A so that the screw head 64 a becomesdeformed from the impaction force F.sub.1 and fits within the centralscore 66 a. Once the screw head 64 a is in the central score 66 a, theoutward excursion of the screw 60 a is prevented by the top lip 68 ofthe central score 66 a.

In FIG. 15C, a third embodiment of the securing means 65 b is showncomprising a screw 60 b having a screw head 64 b with a slightly flangedportion 69 b near the top and a slot 61 b. The central opening 18 hasalong its circumference a recess 66 b for receiving the flanged portion69 b of the screw head 64 b. The securing means 65 b relies on thenatural resiliency of the metal screw head 64 b such that when the screw60 b is being driven by a screw driver, the screw head 64 b flexes inthe direction of the arrows B. In this manner, the flanged portion 69 bof the screw head 64 b slides along the interior of the central opening18 so that the screw head 64 b is below the top lip 68 b of the recess66 b. Once the screw driver is removed from the screw 60 b, the screwhead 64 b returns to its natural state in the direction opposite to thearrows B so that the flanged portion 69 b is within the recess 66 b. Theoutward excursion of the screw 60 is thus prevented by the top lip 68 bwhich blocks the screw head 64 b by catching the flanged portion 69 b.

FIGS. 16A-18 show the instrumentation used for installing the spinalfixation device 10. Referring to FIG. 16A, a driving instrument 80 usedfor inserting the spinal fixation device 10 into the vertebrae V isshown having a hollow tubular shaft 82 which terminates at one end to abottom flat member 84 and terminates to a top flat member 86 at theother end. The bottom flat member 84 is preferably configured so that itconforms to the shape of the top member 14 of the staple member 12.

The driving instrument 80 has a pair of short posts 88 a and 88 bextending from the bottom flat member 84. The posts 88 a and 88 b areoriented on the bottom flat member 84 so as to correspond to theposition of the openings 22 a and 22 b in the upper surface 20 of thetop member 14 of the staple member 12. Each of the posts 88 a and 88 bfit into each of the openings 22 a and 22 b and keep the staple member12 aligned on the bottom flat member 84 of the driving instrument 80. Itis appreciated that the openings 22 a and 22 b in the top member 14 maybe depressions within the surface 20 of the top member 14 or may beholes that pass through the top member 14. In the preferred embodiment,the openings 22 a and 22 b gave a diameter ranging from 1.5 mm to 3.5mm, with 2.5 mm being the preferred diameter.

Referring to FIG. 16B, an alternative embodiment of the drivinginstrument 80′ which is used for inserting into the vertebrae V thespinal fixation device 210, described in detail below in reference toFIG. 26, is shown having a hollow tubular shaft 82′ which terminates atone end to a bottom flat member 84′ and terminates to a top flat member86′ at the other end. The bottom flat member 84′ is rectangular in shapeso that it conforms to the shape of the top member 214 of the spinalfixation device 210.

The driving instrument 80′ has a pair of short posts 88′a, 88′b, 88′cand 88′d extending from the bottom flat member 84′. The posts 88′a-88′dare oriented on the bottom flat member 84′ so as to correspond to theposition of the openings 222 a-222 d of the spinal fixation device 210.Each of the and keep the spinal fixation device 210 aligned on thebottom flat member 84′ of the driving instrument 80′.

Referring to FIG. 17A, an alignment rod 70 comprising a cylindricalshaft 72 having a smooth exterior surface 73 and a threaded end 74 maybe threadably attached to the threaded aperture 45 of the spinal fusionimplant 40 is shown. The alignment rod 70 fits through the centralopening 18 of the spinal fixation device 10 and is used to properlyalign the projections 16 and 17 on each side of the spinal fusionimplant 40 prior to engaging the vertebrae V. Further, the alignment rod70 also serves as a guide post for the drilling template instrument 50described in greater detail below.

Referring to FIG. 17B, as an alternative embodiment of the alignment rod70, a splined alignment rod 70′ that has a finely splined surface 72′along its longitudinal axis and a threaded end 74′ that may be attachedto the threaded aperture 45 of the spinal fusion implant is shown.

Referring to FIG. 18, a drilling template instrument 50 for creating apair of insertion holes 53 a and 53 b in each of the vertebrae V forreceiving each of the projection 16 and 17 respectively is shown. Thedrilling template instrument 50 has a template 52 with a centralaperture 54 therethrough and guide passages 55 and 56 for guiding adrill bit 51 of a drilling tool. Attached to the template 52 is a handle58 which angles away from the template 52 so as not to obstruct the lineof sight of the surgeon and to allow easy access to the template 52 andeasy access to the guide holes 55 and 56 for the drill bit 51. Extendingfrom the center of the bottom surface of the template 52 is a centralmember 59 (similar in structure and function to the central bar 35) formating to an already implanted intervertebral spinal fusion implant 40.The central member 59 interdigitates with the depression 42 of thespinal fusion implant 40 so that the template 52 is properly orientedabout the spinal fusion implant 409 and the guide holes 55 and 56 areproperly oriented with respect to the vertebrae V adjacent to the spinalfusion implant 40. The alignment rod 70 serves as a guide post for thedrill template instrument 50 as it fits through the central aperture 54of the template 52 and aligns the template 52 with respect to thespinal; fusion implant 40 and insures that it is coaxial. The centralaperture 54 of the drilling template instrument 50 is smooth so that ifit is placed over a splined alignment rod 70′ the drilling templateinstrument 50 may be easily rotated about the splined alignment rod 70′into position such that the central member 59 is able to mate andinterdigitate with the depression 44 of the spinal fusion implant 40.

Referring to FIGS. 19-24, the spinal fixation device 10 of the presentinvention is inserted in the following manner: At least one spinalfusion implant 40 is surgically implanted so that it is substantiallywithin the disc space between two adjacent vertebrae V and engages atleast a portion of each of the two adjacent vertebrae V. Once the spinalfusion implant 40 is in place, the alignment rod 70 is attached to thethreaded aperture 45 of the spinal fusion implant 40. The alignment rod70 serves as a guide post for the drilling template instrument 50 as itfits through the central aperture 54 of the template 52 and aligns thetemplate 52 coaxially with respect to the spinal fusion implant 40.

Referring to FIG. 20, once the template 52 is properly aligned and thedrilling template instrument 50 is seated so that the central member 59interdigitates with the spinal fusion implant 40, the insertion holes 53a and 53 b are drilled in each of the adjacent vertebrae V with adrilling instrument having a drill bit 51 with a diameter that issubstantially smaller than the diameter of each the projections 16 and17 of the staple member 12.

Once the drilling of the insertion holes 53 a and 53 b is completed, thedrill template instrument 50 is removed from the spinal fusion implant40 and from the alignment rod 70. The alignment rod 70 is left in placeattached to the threaded aperture 45 of the spinal fusion implant 40.

Referring to FIG. 21, the staple member 12 is placed onto the drivinginstrument 80 used for driving and fixing the staple member 12 into thevertebrae V so that the bottom flat member 84 and the posts 88 a and 88b are aligned with the top member 14 and the depressions 22 a and 22 bof the top member 14. The alignment rod 70 serves as a guide post forthe staple member 12 as it fits through the central opening 18 of thestaple member 12 and aligns the staple member 12 coaxially with respectto the spinal fusion implant 40.

Referring to FIG. 22, once the staple member 12 is properly placed ontothe bottom flat member 84 of the driving instrument 80, the staplemember 12 and the driving instrument 80 are aligned with respect to thealignment rod 70 so that the alignment rod 70 passes through the centralopening 18 of the staple member 12 and is inserted into the centralhollow portion 89 of the driving instrument 80. The staple member 12 andthe driving instrument 80 are then lowered along the alignment rod 70 sothat the sharp distal end 32 of each of the projections 16 and 17 comesinto contact with the external surface of the vertebrae V and is alignedwith the previously drilled insertion holes 53 a and 53 b.

As shown in FIG. 22A, it is preferred that the insertion holes 53 a and53 b be drilled so that when the projections 16 and 17 are inserted intothe holes 53 a and 53 b, the incline planed inner surface 36 of each ofthe projections 16 and 17 contacts the inner wall W of the insertionholes 53 a and 53 b that is closest to the spinal fusion implant 40. Inthis manner a compression force F is created as each of the projections16 and 17 of the staple member 12 is inserted into insertion holes 53 aand 53 b, respectively, compressing the bone of the vertebrae V towardthe spinal fusion implant 40.

Referring to FIG. 23, the staple member 12 is then driven into thevertebrae V by applying a high impaction force to the driving instrument80 with a hammer H or other impacting means against the top flat member86 of the driving instrument 80. The staple member 12 is driven into thevertebrae V such that the projections 16 and 17 are moved forward intothe insertion holes 53 a and 53 b, respectively, until the bottomsurface 30 of the top member 14 of the staple member 12 comes to restagainst the surface of the vertebrae V.

Referring to FIGS. 23-24, the driving instrument 80 is lifted away fromthe alignment rod 70 so that the alignment rod 70 is no longer withinthe central hollow portion 89 of the driving instrument 80. Thealignment rod 70 is unthreaded from the threaded aperture 45 and isremoved from the spinal fusion implant 40. The staple member 12 issecured to the spinal fusion implant 40 with the locking screw 60 whichhas a threaded pattern 62 with a reduced pitch. The reduced pitch of thelocking screw 60 locks the locking screw 60 to the spinal fusion implant40 with minimal turning of the locking screw 60 and prevents anyunwanted loosening. Further, any of the three embodiments of thesecuring means 65, 65 a or 65 b described above in reference to FIGS.15A-15C may be used to further prevent any unwanted loosening andoutward excursion of the screw 60.

Referring back to FIG. 12, once the staple member 12 is driven into thevertebrae V and is secured to the spinal fusion implant 40, the spinalfusion implant 40 is prevented from rotating along its rotational axis Rby its connection to the staple member 12 which is fixated across thedisc space between the vertebrae V. The staple member 12 is preventedfrom backing out from the vertebrae V along the longitudinal axis L byits connection to the spinal fusion implant 40 and by the segmented andratcheted portions 34 of the projections 16 and 17. In this manner, thestaple member 12 and the spinal fusion implant 40 interact to preventthe dislodgement of each other from the vertebrae V in which they areimplanted. Thus, the staple member 12 is made safe against dislodgementby attachment to the spinal fusion implant 40 and the stability of thespinal fusion implant 40 is assured as it is also stabilized by thestaple member 12 and each works in connection with the other to removethe only remaining degree of freedom that would allow for thedisengagement of either. In addition, the incline planed inner surface36 at the distal end 32 of the projections 16 and 17 forces bone towardthe spinal fusion implant 40 along force lines F to further secure thespinal fusion implant 40 and further prevent the dislodgement of thespinal fusion implant 40.

It is appreciated by those skilled in the art that when the bone of thevertebrae V is sufficiently soft, a shorter method (hereinafter referredto as the “Short Method”) of inserting the spinal fixation device 10 ispossible by omitting the steps of drilling the insertion holes 53 a and53 b prior to inserting the staple member 12 into the vertebrae V.

Referring to FIG. 22, in the Short Method, the splined alignment rod 70′that is finely splined along its longitudinal axis is used instead ofthe alignment rod 70. Once the splined alignment rod 70′ has beenattached to the spinal fusion implant 40, the staple member 12 may beplaced over the splined alignment rod 70′ so that the splined alignmentrod 70′ passes through the aperture 18 and into the central aperture 89of the driving instrument 80. The central aperture 89 of the drivinginstrument 80 is correspondingly splined to the splines of the splinedalignment rod 70′ so that the staple member 12 can be aligned withrespect to the spinal implant 40. The alignment of the staple member 12and the driving instrument 80 is maintained as the corresponding splinesof the central aperture 89 interdigitate with the splines of the splinedalignment rod 70′ and prevent the rotation of the staple member 12 aboutthe splined alignment rod 70′. The prevention of rotation about thesplined alignment rod 70′ is especially important when the Short Methodis used to insert the spinal fixation device 10, as no insertion holes53 a and 53 b have been drilled in the vertebrae V. The staple 12 can bedriven directly into the vertebrae V by the application of a highimpaction force to the driving instrument 80 as described above andshown in FIG. 22.

Once the staple member 12 is driven into the vertebrae V, the steps ofthe longer method described above are used to secure the spinal fixationdevice to the spinal fusion implant 40 are the same. The Short Method ofinserting the staple member 12 reduces the amount of time required toinsert and secure the spinal fixation device 10 of the present inventionand thus reduces the overall duration of the spinal fixation surgicalprocedure.

While the present invention has been described with respect to itspreferred embodiment, it is recognized that alternative embodiments ofthe present invention may be devised without departing from theinventive concept.

For example, referring to FIG. 25, a first alternative embodiment of aspinal fixation device 110 having a staple member 112 with a top member114 generally in the shape of an elongated oval having two curved sides124 a and 124 b is shown. In this alternative embodiment, the curvedsides 124 a and 124 b have upper edges 125 a and 125 b, respectively,that are radiused to conform to the external curvature of the vertebraeV thereby creating smooth contoured surfaces as described above for thespinal fixation device 10, the preferred embodiment of the presentinvention. The top member 114 has openings 122 a and 122 b in the uppersurface 120 of the top member 114 and has two projections 116 and 117depending downwardly from the bottom surface 130 of the top member 114at opposite ends of the staple member 112. The projections 116 and 117are the same as the projections 16 described above for the preferredembodiment.

Referring to FIG. 26, a second alternative embodiment of the spinalfixation device 210 having a staple member 212 is shown with a topmember 214 that is generally rectangular 5 in shape and has an uppersurface 220 with openings 222 a, 222 b, 222 c, and 222 d. The top member214 has four projections 216, 217, 218, and 219 depending from itsbottom surface at each of its corners. The projections 216-217 are thesame as the projections 16 and 17 described above in the preferredembodiment. The stop member 2145 has four straight sides 228 a, 228 b,228 c, and 228 d having upper edges 225 a, 225 b, 225 c, and 225 d,respectively, that are radiused to conform to the external curvature ofthe vertebrae V create a smooth surface as described above for thepreferred embodiment. The driving instrument 80′ shown in FIG. 16B isused to insert the spinal fixation device 210.

Referring to FIG. 27, a third alternative embodiment of the spinalfixation device 310 having a staple 312 with a top member 314 that isgenerally triangular is shown. The top member 314 has two projections316 and 317 depending from the bottom surface of the top member 314 thatengage the vertebrae V. Extending from the center of the bottom surfaceof the top member 314 is a central member 390 which is similar to thecentral bar 35 of the preferred embodiment of the spinal fixation device10 in that the central member 390 interdigitates with the depression 44of the spinal fusion implant 40. However, the central bar 390 also hasan extension arm 392 that extends laterally from the top member 314 tospan the diameter of an adjacent spinal fusion implant 41. The extensionarm 392 interdigitates with the depression 44 of the spinal implant 41.The extension arm 392 has a central aperture 394 for receiving a screw60 b used to couple the extension arm 392 to the spinal fusion implant41. In this manner, a single spinal fixation device 310 is capable ofinterdigitating with two adjacent spinal fusion implants 40 and 41 toclock and prevent the rotation and any excursion of the spinal fusionimplants 40 and 41. The fixation of two spinal fusion implants 40 and 41is possible while leaving no protruding metal, such as the top member314, on the side of the spine where the vessels are located in closeapproximation to the vertebrae as is the case with the L₄ and L₅vertebrae where the vessels are located over the left side of thosevertebrae. It is appreciated that any of the securing means 65-65 b,described above may be used to lock the screw 60 b to the extension arm392.

Referring to FIG. 28, a fourth alternative embodiment of the spinalfixation device 410 having a staple member 412 with a top member 414that is generally triangular in shape is shown in the installedposition. The top member 414 is wider and larger than top member 14 asit is used with an implant 440 having a large diameter in the range of22.0 mm to 28.0 mm. The top member 414 needs to be wider when used withimplant 440 in order to provide a central bar 435 of sufficient lengthto interdigitate and mate with the depression 444 of the implant 440 inorder to prevent its rotation. Further, the top member 414 is tapered atportion 416 so as not to cause erosion or pressure against the vesselsthat may be present in the area of the spine adjacent to the portion 416of the top member 414.

Referring to FIGS. 29-32, a fifth alternative embodiment of the spinalfixation device 510 with a staple member 512 having a generallyrectangular top member 514 is shown. The staple member 512 is similar instructure to the staple 212 described above except that the top member514 has multipronged projection blades 516 and 517 depending from itslower surface 530 as shown in FIG. 30. The multipronged projectionblades 516 and 517 have the same function and similar structure as theprojections 16 and 17 described above and include segmented andratcheted portions 534 which are similar in design are function tosegmented and ratcheted portions 34. The multipronged blade projections516 and 517 offer the added advantage of increasing the strength andstability of the staple member 514 once it is inserted into the bone ofthe vertebrae V providing a greater area of engagement of the staplemember 512 to the vertebrae V.

The lower surface 530 has knobs 532 and 534 extending therefrom forengaging and interdigitating with a spinal implant 540 having aninsertion end 541 with openings 542 and 544 for receiving knobs 532 and534 respectively.

Referring to FIGS. 31 and 32, the spinal fusion implant 540 is showninserted within the disc space between two adjacent vertebrae V. Thespinal implant 540 is generally rectangular in shape. The multiprongblade projections 516 and 517 have a width that is approximately equalor slightly less than the width of the spinal fusion implant 540. Onceinserted, the spinal fixation device 510 compresses the bone of thevertebrae V towards the spinal fusion implant 540 as discussed above inreference to FIG. 12. The spinal fixation device 510 may be secured tothe spinal fusion implant 540 with a screw 60 as discussed above.

The spinal fixation device 510 having a staple member 512 is thepreferred embodiment of the present invention for use with amulti-segmental spinal alignment means 600 described in greater detailbelow in that the staple 512 provides a more solid anchoring means thatcan resist greater torsion forces resulting from the application of themulti-segmental spinal alignment means 600 to align the spine.

Alternatively, for all of the embodiments described above, the spinalfixation device 10 of the present invention could be made of resorbablematerials, such as bio-compatible resorbable plastics, that resorb at anappropriate rate such that once the spinal fixation device 10 is nolonger needed (i.e. when spinal fusion is complete) the body wouldresorb the spinal fixation device 10. One such resorbable material ispolygalactone, however any other resorbable plastic or other materialsafely usable within the human body are also within the scope of thepresent invention.

Further, the spinal fixation device could be only in part resorbablesuch that the projections 16 and 17 of the staple member 12 would benon-resorbable and would remain incarcerated in the vertebrae V andsealed off once the resorbable portion of the staple is resorbed by thebody.

Referring to FIGS. 33 and 34, as a further application, the spinalfixation device 510 of the present invention may be used as an anchorfor a multi-segmental spinal alignment means 600, such that amultiplicity of spinal fixation devices may then be interconnected via acable, rod, bar, or plate, so as to achieve or maintain any desiredmulti-segment spinal alignment. In the preferred embodiment, themulti-segmental spinal alignment means 600 comprises more than onespinal fixation device 510 of the present invention placed in seriesalong the spine such that each spinal fixation device 510 spans one discD and engages two adjacent vertebrae V. The spinal fixation device 510is preferred over the other embodiments of the present invention in thatit has a greater area of engagement with the vertebrae V so as toprovide a solid anchoring means for the multi-segmental spinal alignmentmeans 600. However, it is appreciated that other embodiments includingbut not limited to those described herein may be utilized as anchoringmeans for the multi-segmental spinal alignment means 600.

When used as an anchor, each spinal fixation device 510 interdigitateswith and is connected to a spinal fusion implant 610 having an insertionend 612, an interior chamber 614 and is inserted in the disc spacebetween the two adjacent vertebrae. The spinal fusion implant 610 has athreaded blind hole 620 for receiving a threaded post 622 therein. Theblind hole 620 has a casing that is made of strong surgically,implantable material such as, but not limited to titanium. The casing624 extends from the insertion end 612 of the spinal fusion implant 610into the interior central chamber 614. The insertion end 612 has a rigidconstruction that is capable of withstanding high torsion forcesresulting from the tensioning of the multi-segmental spinal alignmentmeans to align segments of the spine. In the preferred embodiment, theinsertion end 612 of the spinal fusion implant has an end portion 626that closes the insertion end 612. The end portion is substantiallythicker than the rest of the spinal fusion implant 610 and in thepreferred embodiment, the end portion 626 has thickness ranging from 1.5mm to 4.0 mm, with 2.5 mm being the preferred thickness.

Referring to FIG. 34, the threaded post 622 has a threaded end 628 witha locking thread pattern that is substantially longer than the lockingthread pattern 62 of the screw 60 described above and a head portion 630having a hole 632 for receiving a rod 634 or a cable therethrough. Thehead portion 630 has a rounded exterior surface to prevent any damagesuch as aortic erosion to the vessels in the area adjacent to the spine.In the preferred embodiment the threaded post has a diameter rangingfrom 3.0 mm to 6.0 mm, with 4.5 mm being the preferred diameter and hasa length ranging from 15.0 mm to 25.0 mm, with 20.0 mm being thepreferred length. The head portion 630 extends at a height above the topmember 514 of the spinal fixation device 510 of approximately 8.0 mm to16.0 mm, with 12.0 being the height preferred once it is threadablyattached to the spinal fusion implant 610 such that it does notsignificantly protrude from the spinal column into the tissue andvessels adjacent thereto.

Once the threaded post 622 is attached to the spinal fusion implant 610,the head portion 630 of each threaded post 622 are connected to oneanother by the rod 634 having a sufficient diameter to fit through thehole 632 of each head portion 630. The rod 634 has at least a portionthereof that is threaded so that a plurality of lock nuts 638 may beused to secure the rod 634 to the head portions 630. The lock nuts 638may also be used as length adjusting means to adjust the length of therod 634 between head portions 630 so that segmental portions of thespine may be held closer together or held further aport for the purposesof aligning the spine. It is appreciated that a plurality ofmulti-segmental spinal alignment means 600 may be placed in serieseither on one side or on opposite sides of the spine, such that one sideof the spine may be extended while the other side may be held stationaryor may be compressed in order to achieve proper spinal alignment. Themulti-segment spinal alignment may be maintained by keeping the rodtensioned with the lock nuts 638 or by any other means well known bythose skilled in the art. It is also appreciated that in place of a rod634 a cable, a plate or any other means well known by those skilled inthe art may be used to interconnect the multi-segmental spinal alignmentmeans.

Referring to FIG. 35, a sixth alternative embodiment of the spinalfixation device of the present invention is shown and generally referredto by the numeral 710. The spinal fixation device 710 comprises a topmember 714 that is similar to the top member 14 described above, exceptthat it does not have projections 16 and 17 extending from the bottomsurface. Like numbers are being used to designate identical features ofthe top members 14 and 714.

In the top member 714, instead of having projections 16 and 17,independent projection members 716 and 717 in the form of screws areused to secure the top member 714 of the spinal fixation device 710 tothe vertebrae V of the spine. The projection screw members 716 and 717each terminate in a sharp distal end 720 and 722 respectively, have athreaded portion 723, and have screw heads 724 and 726 for engaging ascrew driver or similar driving instrument.

The top member 714 has a hole 728 on one end and a hole 730 at its otherend through which each of the projection screw members 716 and 717respectively, may pass. The projection screw members 716 and 717 passthrough the holes 728 and 730 to engage the vertebrae V. Each of theholes 728 and 730 has a concentric counter sunk recess 732 for receivingand seating the screw heads 724 and 726 of the projection screw members716 and 717 so that the screw heads 724 and 726 are flush or below thetop surface 20 of the stop member 714 once inserted into the vertebraeV.

As the projection screw members 716 and 717 are threaded, they can berotationally advanced into the vertebrae instead of by way of animpaction force such that the potential for damage to the vertebrae V isreduced. The threads of the threaded portion 723 follow one another asthe projection screw members 716 and 717 are being screwed into the bonesuch that the integrity of the vertebrae V is preserved. Also, as theprojection screw members 716 and 717 are independent from the top member714, the penetration depth of the spinal fixation device 710 into thebone of the vertebrae V may be easily altered by selecting differentsized projection screw members 716 and 717 appropriate for theparticular vertebrae being fused. Further, it is possible to configurethe holes 728 and 730 in the top member 714 such that the projectionscrew members 716 and 717 may be inserted into the vertebrae V from anumber of different angles relative to the top member 714.

Adjacent and proximate to each of the holes 728 and 730 are threadedopenings 740 and 742, respectively, for receiving locking screws 744 and746 respectively. Each of the locking screws 744 and 746 have a headportion 750 and a locking thread portion 754 for threadably and lockablyengaging the threaded openings 740 and 742. The locking screws 744 and746 are attached to the top member 714 after the projection screwmembers 716 and 717 have been inserted into the vertebrae V. At least apart of the head portion 750 and 752 blocks and preferably makes contactwith the screw projections 716 and 717 to prevent any unwanted looseningand outward excursion of the screw projections 716 and 717.

It is appreciated that the projection members 716 and 717, instead ofbeing threaded screws, may have a number of other configurations suchas, but not limited to, the configurations of the projections describedabove for the various embodiments of the present invention. If theprojections members 716 and 717 are ratcheted instead of being threaded,they can be driven into the vertebrae V with a driving instrument andimpaction force as described above for the method of the presentinvention.

While the present invention has been described with respect to itspreferred embodiment and a number of alternative embodiments, it isrecognized that additional variations of the present invention may bedevised without departing from the inventive concept and scope of thepresent invention.

27

1. A spinal device for stabilizing two adjacent cervical vertebralbodies of the human spine, each of the adjacent cervical vertebralbodies having an anterior aspect and an external curvature, said devicecomprising: a screw having a head, a shaft, a mid-longitudinal axis anda length along the mid-longitudinal axis, said shaft including a thread;and a member having an upper surface, a lower surface opposite saidupper surface, and a length sufficient to span a disc space between thetwo adjacent cervical vertebral bodies, said lower surface being adaptedto contact the anterior aspect of each of the two adjacent cervicalvertebral bodies, said member being curved to conform to the externalcurvature of the adjacent cervical vertebral bodies, said memberincluding a screw hole having a central longitudinal axis and a depthfrom said upper surface to said lower surface along the centrallongitudinal axis, the depth of said screw hole being less than thelength of said screw, said screw hole intersecting with said uppersurface to form an entrance having an inner perimeter, said uppersurface including a recess, an integral portion of said upper surfacethat defines both a portion of said entrance and a portion of saidrecess being bendable from an open position that permits insertion ofsaid head of said screw into said screw hole to a closed position wheresaid integral portion overlaps a portion of said head of said screw toprevent the outward excursion of said screw from said screw hole.
 2. Thedevice of claim 1, wherein said member includes a width transverse tothe length of said member, said member including opposite sides alongthe length, one of said sides having a portion curved partially aroundthe central longitudinal axis of said screw hole.
 3. The device of claim1, wherein said lower surface of said member includes two ratchetedprojections at opposite ends of said member.
 4. The device of claim 1,wherein said thread of said screw has a maximum diameter, said screwincluding a non-threaded portion with a diameter equal to the maximumdiameter of said thread of said screw.
 5. The device of claim 1, incombination with a spinal implant, said screw being adapted to couplesaid member to said spinal implant.
 6. The device of claim 1, whereinsaid inner perimeter of said entrance extends completely around thecentral longitudinal axis of said screw hole.
 7. The device of claim 1,wherein said recess is completely separate and spaced-apart from saidscrew hole.
 8. The device of claim 1, wherein said integral bendableportion of said member has a bending axis transverse to the centrallongitudinal axis of said screw hole.
 9. The device of claim 1, whereinsaid recess is a notch.
 10. The device of claim 1, in combination withan instrument for bending said integral bendable portion.
 11. The deviceof claim 1, wherein said integral bendable portion is deformable. 12.The device of claim 1, in combination with a fusion promoting material.13. A spinal device for stabilizing two adjacent cervical vertebralbodies of the human spine, each of the adjacent cervical vertebralbodies having an anterior aspect and an external curvature, said devicecomprising: a screw having a head, a shaft, a mid-longitudinal axis anda length along the mid-longitudinal axis, said shaft including a thread;and a member having an upper surface, a lower surface opposite saidupper surface, and a length sufficient to span a disc space between thetwo adjacent cervical vertebral bodies, said lower surface being adaptedto contact the anterior aspect of each of the two adjacent cervicalvertebral bodies, said member being curved to conform to the externalcurvature of the adjacent cervical vertebral bodies, said memberincluding a screw hole having a central longitudinal axis and a depthfrom said upper surface to said lower surface along the centrallongitudinal axis, the depth-of said screw hole being less than thelength of said screw, said screw hole intersecting with said uppersurface to form an entrance having an inner perimeter, a portion of saidinner perimeter of said entrance being deformable from a circular openposition that permits insertion of said head of said screw into saidscrew hole to a closed position where said portion of said innerperimeter is closer to the central longitudinal axis of said screw hole,said portion of said inner perimeter in the closed position overlying aportion of said head of said screw to prevent the outward excursion ofsaid screw from said screw hole.
 14. The device of claim 13, whereinsaid member includes a width transverse to the length of said member,said member including opposite sides along the length, one of said sideshaving a portion curved partially around the central longitudinal axisof said screw hole.
 15. The device of claim 13, wherein said lowersurface of said member includes two ratcheted projections at oppositeends of said member.
 16. The device of claim 13, wherein said thread ofsaid screw has a maximum diameter, said screw including a non-threadedportion with a diameter equal to the maximum diameter of said thread ofsaid screw.
 17. The device of claim 13, in combination with a spinalimplant, said screw being adapted to couple said member to said spinalimplant.
 18. The device of claim 13, wherein said inner perimeter ofsaid entrance extends completely around the central longitudinal axis ofsaid screw hole.
 19. The device of claim 13, further comprising arecess, said deformable portion of said inner perimeter separating saidrecess from said screw hole.
 20. The device of claim 19, wherein saidrecess is a notch.
 21. The device of claim 13, wherein said deformableportion of said inner perimeter deforms about a bending axis transverseto the central longitudinal axis of said screw hole.
 22. The device ofclaim 13, in combination with an instrument for moving said deformableportion of said inner perimeter.
 23. The device of claim 13, incombination with a fusion promoting material.
 24. A spinal device forstabilizing two adjacent cervical vertebral bodies of the human spine,each of the adjacent cervical vertebral bodies having an anterior aspectand an external curvature, said device comprising: a member having anupper surface, a lower surface opposite said upper surface, and a lengthsufficient to span a disc space between the two adjacent cervicalvertebral bodies, said lower surface being adapted to contact theanterior aspect of each of the two adjacent cervical vertebral bodies,said member being curved to conform to the external curvature of theadjacent cervical vertebral bodies, said member including a screw holehaving a central longitudinal axis and a depth from said upper surfaceto said lower surface along the central longitudinal axis; and adeformable securing means for locking a head of a screw to said member.25. The device of claim 24, wherein said securing means includes adeformable portion of said member proximate said screw hole.
 26. Thedevice of claim 24, wherein said securing means includes a bendableportion of said member proximate said screw hole.
 27. The device ofclaim 24, wherein said securing means includes a portion of a recessadjacent said screw hole.
 28. The device of claim 24, wherein saidmember includes a width transverse to the length of said member, saidmember including opposite sides along the length, one of said sideshaving a portion curved partially around the central longitudinal axisof said screw hole.
 29. The device of claim 24, wherein said lowersurface of said member includes two ratcheted projections at oppositeends of said member.
 30. The device of claim 24, in combination with afusion promoting material.